共查询到20条相似文献，搜索用时 31 毫秒
1.
In this paper, the dynamic response simulation of heavy cargo suspended by a floating crane is performed. The dynamic equations of the motions of the floating crane and the heavy cargo must be considered by the coupled equations because the floating crane and the heavy cargo are connected by wire ropes and provide force and a moment for each other. Hence, the dynamic equations of motion are set up for considering the 6-degrees-of-freedom floating crane and the 6-degrees-of-freedom cargo based on multibody system dynamics. The nonlinear terms in the equations of motion are considered. In addition, the nonlinear hydrostatic force, the linear hydrodynamic force, the wire rope force, and the mooring force are considered as the external forces. Finally, we estimate the motion of the floating crane and the heavy cargo and also calculate the tension of the wire rope between the two. 相似文献
2.
具有链—缆—链结构的复合系泊链缆因其相对于全钢链质量和成本上的优势而在深水系泊中得以广泛应用。基于细长杆理论采用有限差分法建立了可以考虑链—缆—链结构的复合系泊缆数值模型,将其应用于不同工况下全钢链和复合链缆运动的数值模拟中,并开展了验证。首先,将单根钢链顶张力数值模拟结果与不同工况下的模型试验结果进行了对比,验证了数值预报程序应用于全钢链的准确性。然后,对于复合系泊链缆开展了静刚度和动刚度迭代数值模拟,并将模拟结果同已发表文章中的算例结果进行比较,验证了该数值模型在复合链缆模拟上的准确性。发现对于单根钢锚链的验证,激励半径越大,激励周期越小,一个周期内顶张力幅值及其极差越大,钢链运动就越剧烈。对于链—缆—链式复合系泊链缆的验证,发现静刚度迭代中数值模拟结果与算例结果差异较小;对于动刚度迭代,除个别大幅慢漂工况外,两者有较高的吻合;且激励周期越小,激励半径越大,复合系泊链缆顶张力越大,弹性模量越小,运动越剧烈。对于聚酯缆刚度的敏感性分析,发现改变动刚度经验公式参数的情况下,杨氏模量的静刚度迭代和动刚度迭代结果误差分别最大达到了60.81%和68.21%,因此合成纤维材料特性对复合系泊链... 相似文献
3.
FSRU码头系泊模型实验与数值模拟研究 总被引：1，自引：0，他引：1
FSRU在恶劣环境条件下的作业和安全停靠性能与系泊缆张力、靠垫挤压应力、船体6自由度运动等参数有关。针对FSRU码头处海洋环境条件,进行FSRU不同装载状况的模型实验,获得FSRU的6自由度运动及其系泊载荷的动力特性。基于三维辐射和绕射理论,使用Sesam软件进行频域计算,以此为基础在相应海洋环境条件下进行时域耦合分析,获得FSRU 6自由度运动、系泊载荷、靠垫应力等参数的响应时历。结果表明:30%装载、横浪条件下FSRU的运动响应最大,系泊缆张力未达到破断值,靠垫压力超过其压缩60%时的载荷;模型实验对FSRU运动响应和系泊缆张力的预测结果可信,靠垫受力情况需要数值仿真进行辅助研究。 相似文献
4.
Design Curves for Mooring Lines of Turret Mooring Systems 总被引：1，自引：0，他引：1
Gao Jie Tan Jiahua Chen Xiaohong
Associate Professor Shanghai Jiao Tong University Shanghai
Professor Shanghai Jiao Tong University Shanghai
Lecturer Shanghai Jiao Tong University Shanghai 《中国海洋工程》1997,(4)
This paper presents a series of design curves to aid in the selection of turret mooring systemsfor tankers based Floating Production Storage and Offloading(FPSO)systems.These curves are appropri-ate to water depths ranging from 100m to 600m.The curves can be used as a preliminary design tool,al-lowing the designer to quickly evaluate alternative mooring system configurations,including the numberof mooring lines,the characteristics of chain and wire rope to be deployed and the initial tension.With aknowledge of the total environmental force and vessel motion characteristics,the designer can determinethe appropriate system for closer evaluation. 相似文献
5.
由于聚酯缆绳具备优异的力学性能,促使以其为主体系缆的绷紧式系泊系统得以广泛应用和发展。但聚酯系缆具有复杂的黏弹性和黏塑性,且由于在安装和使用过程中可能产生不同程度的损伤,使得聚酯系缆的动刚度特性发生演变,从而对系泊系统的动力响应产生直接影响。以一系泊于1 020 m水深的Spar平台为例,运用ABAQUS软件建立了由聚酯缆绳组成的系泊系统有限元模型,并利用ABAQUS子程序将损伤缆绳动刚度经验公式进行导入计算,以更好地反映系缆真实的动刚度变化。基于该有限元模型,计算了在相同水流、波浪工况下,不同损伤度、不同损伤系缆的系缆张力历程和平台的横荡、纵荡位移响应,分析了不同损伤度、不同损伤系缆对系缆张力及平台位移的影响。这些成果对把握绷紧式系泊系统在聚酯系缆有损伤情况下的非线性动力响应及其安全应用具有重要的参考价值。 相似文献
6.
Based on the lumped-mass method and rigid-body kinematics theory, a mathematical model of a gravity cage system attacked by irregular waves is developed to simulate the hydrodynamic response of cage system, including the maximum tension of mooring lines and the motion of float collar. The normalized response amplitudes (response amplitude operators) are calculated for the cage motion response in heave and surge, and the mooring line tension response, in regular waves. In addition, a statistical approach is taken to determine the motion and tension transfer functions in irregular waves. In order to validate the numerical model of a gravity cage attacked by irregular waves, numerical predictions have been compared with the experimental observations in the time and frequency domain. The effect of wave incident angle on the float collar motion, mooring line tension and net volume reduction of the gravity cage system in irregular waves is also investigated. The results show that at high frequencies, the cage system has no significant heave motion. It tends to contour itself to longer waves. The variation amplitude of mooring line forces decreases as the wave frequency increases. With the increasing of wave incident angle, the horizontal displacement of the float collar increases. 相似文献
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8.
Accurate prediction of the offshore structure motion response and associate mooring line tension is important in both technical applications and scientific research. In our study, a truss spar platform, operated in Gulf of Mexico, is numerically simulated and analyzed by an in-house numerical code ‘COUPLE'. Both the platform motion responses and associated mooring line tension are calculated and investigated through a time domain nonlinear coupled dynamic analysis. Satisfactory agreement between the simulation and corresponding field measurements is in general reached, indicating that the numerical code can be used to conduct the time-domain analysis of a truss spar interacting with its mooring and riser system. Based on the comparison between linear and nonlinear results, the relative importance of nonlinearity in predicting the platform motion response and mooring line tensions is assessed and presented. Through the coupled and quasi-static analysis, the importance of the dynamic coupling effect between the platform hull and the mooring/riser system in predicting the mooring line tension and platform motions is quantified. These results may provide essential information pertaining to facilitate the numerical simulation and design of the large scale offshore structures. 相似文献
9.
采用集中质量法研究了绷紧式系泊系统中系缆由于松弛-张紧过程产生的冲击张力。建立系泊缆绳离散的集中质量模型,对其独立单元进行受力分析并建立了单元的运动方程。给定缆绳上端点简谐激励,通过Ansys中的Aqwa模块,分析了缆绳的运动响应;针对缆绳运动响应过程中的三种状态进行了模拟计算,探讨了冲击张力产生的条件;研究了缆绳初始预张力、上端点激励幅值和频率、拖曳力系数、弹性模量以及单位长度质量对动态张力的影响。研究结果表明:这些影响因素不仅会影响缆绳动态张力的大小,也会对缆绳中的冲击张力产生一定的影响。 相似文献
10.
内孤立波中半潜平台动力响应特性 总被引：1，自引：1，他引：0
基于内孤立波mKdV理论,采用时域有限位移运动方程,结合改进的Morison公式,研究了两层流体中内孤立波与带分段式悬链系泊约束半潜平台的相互作用问题。针对东沙群岛南部海域附近某实测内孤立波特征参数,计算分析了在该内孤立波作用下SEDCO-700型半潜平台的内孤立波载荷、运动响应及其系泊张力的变化特性。研究表明,内孤立波不仅会对半潜平台产生突发性冲击载荷作用,使其产生大幅度水平漂移运动,并导致其系泊张力显著增大,因此在半潜平台等深海平台的设计与应用中,内孤立波的影响是不可忽视的。 相似文献
11.
Mooring tension and motion characteristics of a submerged fish reef with net in waves and currents using numerical analysis 总被引：2，自引：0，他引：2
A numerical model was used to analyze the motion response and mooring tension of a submerged fish reef system. The system included a net attached to a rigid structure suspended up from the bottom with a single, high tension mooring by fixed flotation. The analysis was performed by using a Morison equation type finite element model configured with truss elements. Input forcing parameters into the model consisted of both regular and irregular waves, with and without a steady current. Heave, surge and pitch dynamic calculations of the reef structure were made. Tension response results of the attached mooring line were also computed. Results were analyzed in both the time and frequency domain in which appropriate, linear transfer functions were calculated. The influence of the current was more evident in the tension and heave motion response data. This is most likely the result of the large buoyancy characteristics of the reef structure and the length of the mooring cable. Maximum mooring component tension was found to be 13.9 kN and occurred when the reef was subjected to irregular waves with a co-linear current of 1.0 m/s velocity. The results also showed that the system had little damping (in heave) with damped natural periods of 2.8 s. This combination of system characteristics promotes a possible resonating situation in typical open sea conditions with similar wave periods. 相似文献
12.
The synthetic fiber ropes such as the aramid and polyester ones applied to deepwater mooring systems always exhibit obvious time-dependent like creep and recovery behaviors due to the viscoelasticity and viscoplasticity of the materials, which affect not only the modulus evolution of mooring ropes but also the dynamic response and fatigue performance of the taut-wire mooring system. In the present work, the Schapery's theory combined with Owen's one-dimensional rheological model is proposed to describe both viscoelastic and viscoplastic behaviors of the aramid and polyester fiber ropes. In the viscoelastic part, the Prony series is chosen to describe the transient compliance, which is more accurate than other functions especially under complex loadings; in the viscoplastic part, the adopted viscoplastic function is more suitable for the strain hardening behaviors and the stable state of the materials under variable stress levels. Detailed methods for identifying the model parameters are proposed, which can be applied to any component of the fiber rope such as the fiber, yarn, sub-rope and rope. The present model is capable of quantitatively capturing the change-in-length properties of fiber ropes reported by Flory et al., and can be easily incorporated in the commercial software for mooring analysis. In order to examine the feasibility and precision of the model, the viscoelastic and viscoplastic strains are calculated and compared with experimental and other numerical simulation results. It is observed that there is a good agreement between the predicted and experimental data, and the physically irrational results caused by the key parameter DP previously noticed by Chailleux and Davies can be well eliminated. The present model provides a better tool to further understand the nonlinear behaviors of synthetic fiber ropes for deepwater moorings. 相似文献
13.
This paper presents a simulation model based on the finite element method. The method is used to analyze the motion response and mooring line tension of the flatfish cage system in waves. The cage system consists of top frames, netting, mooring lines, bottom frames, and floats. A series of scaled physical model tests in regular waves are conducted to verify the numerical model. The comparison results show that the simulated and the experimental results agree well under the wave conditions, and the maximum pitch of the bottom frame with two orientations is about 12o. The motion process of the whole cage system in the wave can be described with the computer visualized technology. Then, the mooring line tensions and the motion of the bottom frame with three kinds of weight are calculated under different wave conditions. According to the numerical results, the differences in mooring line tensions of flatfish cages with three weight modes are indistinct. The maximum pitch of the bottom frame decreases with the increase of the bottom weight. 相似文献
14.
《Marine Models》1999,1(1-4):103-157
Mooring Design and Dynamics is a set of Matlab® routines that can be used to assist in the design and configuration of single point oceanographic moorings, the evaluation of mooring tension and shape under the influence of wind and currents, and the simulation of mooring component positions when forced by time-dependent currents. The static model will predict the tension and tilt at each mooring component, including the anchor, for which the safe mass will be evaluated in terms of the vertical and horizontal tensions. Predictions can be saved to facilitate mooring motion correction. Time-dependent currents can be entered to predict the dynamic response of the mooring. The package includes a preliminary database of standard mooring components which can be selected from pull down menus. The database can be edited and expanded to include user specific components, frequently used fasteners/wires etc., or unique oceanographic instruments. Once designed and tested, a draft of the mooring components can be plotted and a list of components, including fasteners can be printed. 相似文献
15.
非通航孔桥墩自适应拦截网防撞装置实船拦截试验与水动力计算 总被引：1，自引：0，他引：1
针对非通航孔桥墩,研发了一种自适应拦截网防船舶撞击装置,主要由系泊大浮体、系泊锚链和固定锚、自适应小浮筒、拦截网、恒阻力缆绳以及触发钢索所组成。阐述了该防撞装置设计原理,即偏航船舶撞击该防撞装置,小浮筒会带动拦截网自适应地从水平状态竖起展开,包裹住来撞船首,再通过相连浮体的运动阻力和恒阻力缆绳来吸收船舶动能,拦截住船舶,保护非通航孔桥墩安全。随后介绍在福建平潭海峡大桥引桥附近海域实施的实船撞击自适应拦截网防撞装置的大型试验,试验结果显示:自适应拦截网成功升起,船舶被安全拦截,从而实验证实了设计原理与设计方案的可行性和可靠性。最后,采用大型水动力分析软件AQWA对防撞装置拦截船舶过程进行数值模拟,模拟结果与实验结果基本一致,说明了数值仿真具有较好的计算精度和可靠性,能够为该防撞装置的结构设计与优化提供重要的参考。 相似文献
16.
Qiao Dong-sheng Yin Li Yan Jun Tang Wei Ning De-zhi Li Bin-bin Ou Jin-ping 《中国海洋工程》2021,35(5):700-711
The maximum predicting error of the commonly used passive truncated mooring system method may reach 30% due to the difference of dynamic characteristics between the truncated and full-depth mooring line. In this paper, the experimental strategy called three-parameter (displacement, velocity and acceleration) active control method at the truncated point of mooring line is established to implement the synchronous equivalent of motion and force, and the realization of active truncated mooring system for model test is studied theoretically. The influences of three-parameter and one-parameter (displacement) active control strategies on the compensation effects are compared by numerical study. The results show that the established three-parameter active control method can feasibly realize the static and dynamic equivalent of truncated and full-depth mooring system, laying a good foundation for the following physical model test of active truncated mooring system.
相似文献17.
我国南海海域海洋环境条件复杂且海水密度垂直层化现象显著,内孤立波活动频繁,因内孤立波而造成海洋开采平台破坏的案例屡见不鲜。依托水动力计算软件AQWA二次开发功能,采用Kdv方程,借助Fortran语言将深水半潜式平台立柱、浮箱、系泊系统3部分的内孤立波作用力叠加到外力项中,联合求解半潜式平台的6自由度动力响应特性。数值模拟结果表明,在内孤立波作用下,半潜式平台的运动及系泊线张力均受到了显著的影响。在不考虑系泊系统受内孤立波作用时,平台在纵荡和横荡方向上产生较大的漂移运动,最大偏移量较无内孤立波情况下增加了8倍;系泊线最大张力提高了17%,增加了系泊线断裂的风险。在考虑系泊系统受内孤立波作用时,平台的纵荡和横荡运动响应在原响应基础上继续提高15%,但是系泊线张力变化不大。内孤立波不同浪向下的平台纵荡和横荡响应相差也很明显;系泊系统合力在不同方向上的大小决定了平台不同方向上运动的大小。 相似文献
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19.
《Applied Ocean Research》2007,29(1-2):45-54
Catenary mooring lines are typically subjected to bimodal loads, comprising of a wave frequency (WF) component due to the first-order wave forces and a low frequency (LF) component induced by the second-order wave forces. For moored vessels, the LF forces due to current and wind also play a role. Only dynamic wave loads are considered herein, while current and wind loads are modeled as constant forces. Because of the nonlinearities of the mooring line characteristics, the dynamic line tension and the second-order responses, both the WF and LF line tensions are in principle nonGaussian. These facts make it difficult to estimate the combined fatigue damage of mooring lines in the frequency domain. A fatigue combination rule based on the Jiao and Moan’s theory has been extended to cover the nonGaussian case. The purpose of this paper is to improve and validate the frequency-domain method by time-domain analysis based on a simplified, but accurate mechanical model of the dynamic line tension. Improvements on the LF and combined fatigue damage estimation have been made by considering the nonsymmetrical property of the LF line tension distribution. Both the WF and LF mooring line tensions due to wave loading have been simulated in the time domain for different sea states and the combined fatigue damage has been estimated by using the rainflow cycle counting algorithm. The accuracy of the frequency-domain method for estimating the bimodal nonGaussian fatigue damage of mooring lines has been verified by the time-domain simulations and is considered to be acceptable. 相似文献
20.
As current attention of the offshore industry is drawn by developing pilot farms of Floating Wind Turbines (FWTs) in shallow-water between 50m and 100m, the application of nylon as a mooring component can provide a more cost-effective design. Indeed, nylon is a preferred candidate over polyester for FWT mooring mainly because of its lower stiffness and a corresponding capacity of reducing maximum tensions in the mooring system. However, the nonlinear behaviors of nylon ropes (e.g. load-elongation properties, fatigue characteristics, etc.) complicate the design and modeling of such structures. Although previous studies on the mechanical properties and modeling of polyester may be very good references, those can not be applied directly for nylon both on testing and modeling methods. In this study, first, an empirical expression to determine the dynamic stiffness of a nylon rope is drawn from the testing data in the literature. Secondly, a practical modeling procedure is suggested by the authors in order to cope with the numerical mooring analysis for a semi-submersible type FWT taking into account the dynamic axial stiffness of nylon ropes. Both the experimental and numerical results show that the tension amplitude has an important impact on the dynamic stiffness of nylon ropes and, as a consequence, the tension responses of mooring lines. This effect can be captured by the present modeling procedure. Finally, time domain mooring analysis for both Ultimate Limit State (ULS) and Fatigue Limit State (FLS) is performed to illustrate the advantages and conservativeness of the present approach for nylon mooring modeling. 相似文献